Media devices or telecommunication end point devices such as telephones and videophones that work across networks require some mechanism whereby they can efficiently share the network infrastructure with other network devices taking into consideration the requirements of media streams between the media devices and how they differ from those of ordinary data such as from computers in normal use. Media streams, particularly for videophone calls, require consistent high bandwidth on the shared network between end point devices to be acceptable. This is because current compressed media streams are vulnerable to lost packets because information in the current packet often makes reference to information which should have been received in a previous packet. So, if that previous packet is not delivered, then a decoder of the receiving end point device must somehow recover from the situation either by requesting retransmission of the lost information or filling in with made-up information. In either case, the user of the end point device will observe a discontinuity of video or audio which is not desirable. In contrast, ordinary data from computers, such as from internet surfing, e-mailing and file upload and download has variations in bandwidth requirements depending on the task being carried out, and it can be acceptable to have varying bandwidth availability on the shared network.
FIG. 1 illustrates such a known shared network 10. It includes a media device 2, in this example, a video phone, connected to the Internet 1 via a bandwidth-constrained link 4 controlled by a router 6. A computer, in this example, in the form of a personal computer (PC) or desktop computer 5 is also connected to the Internet 1 via the same bandwidth-constrained link 4 controlled by the same router 6. There are another two media devices also, in this example, video phones 3 and 8 connected to the Internet 1 via another bandwidth-constrained link 9 controlled by another router 12. One of the media devices 2 sends media to one of the other media devices 3, but the competing device on the network, the PC 5, also attempts to send information to the Internet over the same bandwidth constrained link 4 as the media device 2 and at the same time. Under these circumstances, some compromise must be reached whereby the importance of the various data streams from the media device 2 and the PC 5 will determine the proportion of bandwidth that should be dedicated to them on the bandwidth-constrained link 4.
In known arrangements, media devices 2,3,8 currently have a “self-centred” view of bandwidth. They will typically start transmitting at a particular bit rate as if they are the only device on the network 10 using a bandwidth-constrained link 4,12 and will “back off” or reduce their bit rate as they experience the effects of competition for resources by detecting dropped packets. This initial loss of packets gives a user of the media device a frustrating and unsatisfactory first impression either through call set-up delays or broken first images until the bit rate has settled down to a workable rate.